This proposal is for a 5-year study to examine the hypothesis that lowered levels of objectively measured exercise capacity and pulmonary function are important predictors of reduced age-related levels of physical performance after adjustment for lifestyle (e.g., exercise habits), disease morbidity and smoking. The study also will assess the effects of aging itself on changes in exercise capacity and lung function after adjustment for important covariates. Finally, the study will assess the extent to which social variables (e.g., living arrangements) affect the association between age, exercise and lung function on levels of physical performance (particularly ADL and IADL). A community-based sample of approximately 3673 non-institutionalized male and female residents of Sonoma, CA aged greater than or equal to 55 years will be enrolled. Baseline home interviews and laboratory-based assessments will be conducted. The home interview will address self- reported and direct measures of physical performance, disease morbidity, current and past exercise habits, history of smoking and alcohol consumption, level of cognitive function, symptoms of depression, living arrangements and other measures of social networks and social support. Exercise capacity (time on treadmill, O2 consumption and other physiological variables measured during treadmill exercise) and pulmonary function (maximum expiratory flow-volume curves, inspiratory and expiratory pressures) will be measured in a community-based laboratory. Two subsequent contacts will be made with the respondents. Approximately 16 months after baseline, a second home interview will be conducted. A third contact will be made 16 months later to administer the home interview and to conduct a second laboratory evaluation. In addition to the determination of the extent to which baseline exercise capacity and lung function predict subsequent levels of physical performance, this study will provide data essential for the development of studies to test strategies to improve the health and adaptive capacities of the elderly.